An aircraft seat map or seating chart is a diagram of the seat layout inside a passenger airliner. They are often published by airlines for informational purposes and are of use to passengers for selection of their seat at booking or check-in. Seat maps usually indicate the basic seating layout; the numbering and lettering of the seats; and the locations of the emergency exits, lavatories, galleys, bulkheads and wings. Airlines that allow internet check-in frequently present a seat map indicating free and occupied seats to the passenger so that they select their seat from it. In addition to the published seat maps from airliners, there are a number of independent websites which also publish seat maps along with reviews of individual seats, noting the seats that are particularly good (extra legroom, quiet cabin, etc.) or bad (lack of recline, unusually cramped, missing window, etc.). Published by airlines Most of the airlines publish the seat configurations for their aircraft, but the quality of these seat maps is sometimes questionable. Some of the details and information about seats are confusing. Usually airlines do not publish seat maps for every aircraft, only for the larger aircraft and for the ones flying on frequent routes. When passengers complete an online booking, or check in online, they are often also presented with an aircraft seat map. However, this data is typically sourced from the original text-only seat maps on computer reservation systems such as Sabre, where the seat map is simply held as a two-dimensional array and as such can only display a grid of seats, as opposed to the more varied layouts now used in first and business class. Experimental psychologist Mike Nicholls et al. (2013) have reported that when people book seats online, they exhibit a leftward preference for seats on an aircraft, but a rightward preference for seats at the theatre. Published by specialised websites In addition to those published seat maps which can be found on airline websites, there are some other websites that publish aircraft seat maps for almost all commercial carriers. Seat maps that can be found on these sites usually have more details, and some websites have comments from passengers with advantages and disadvantages about each seat. The accuracy and editorial independence of specialised websites showing seat maps have also been questioned. SeatGuru has come under scrutiny since it was sold to the online booking agent Expedia for